By now, the beans in your garden should be filling out and producing a few baskets of crisp legumes. If some of the plants' leaves have spots and crinkles, though, your fresh side dish could be in jeopardy.
Those little black spots on the leaves and pods could be anthracnose. This fungus travels on wind and water, and can be spread on tools, seeds, containers, or even shoes. The black sunken ulcers may appear on many kinds of plants. Beans, roses, grapes, brambles, and members of Cucurbita like watermelon are very prone to anthracnose.
If you spot these spots on your plants, wait unit the soil is dry, then pull out the plants. Try to keep the leaves of neighboring plants dry so the fungus doesn't spread. Keep the leaf debris picked up around the plants and toss all of their litter in the burn barrel and look for disease-resistant varieties to plant next year.
Bean mosaic disease is in the soil. Affected leaves look crinkled and yellow, and don't produce many pods. The best way to protect a garden from mosaic is to look for disease-resistant seeds. The mosaic virus is usually spread by tiny aphids on the plants. Pull out the plants immediately and try to lure some ladybugs to feed on the aphids.
Wilty beans could also mean they have a case of fusarium wilt. This attacks the roots and causes the plants to grow very slowly. Because the roots are weak, the plants start to wilt on hot days. Some leaves may even turn yellow. Fusarium is a fungus that can affect many kinds of plants like tomato, asparagus, cabbage, corn, cucumber, and watermelon. But each strain usually stays with its host. For example, the fusarium causing beans to wilt probably won't affect the tomatoes you plant in the same spot next year.
If beans get a bad case of wilt or mosaic, pull the affected plants out of the ground and burn them. Don't till affected plants back into the garden this fall because that could add to the problem for next summer.
Plant beans in a different spot each year. Some soil-borne diseases can stick around from season to season.
If you see holes in the bean leaves, bean leaf beetles might be to blame. You might think there is enough foliage to go around, but these little beetles can do some serious damage. If plants get infested early in the season, they might not survive the attack. Insecticides will help keep the beetles away.
You also might spot a little yellow fuzzy bug on bean plants. Mexican bean beetles look like ladybugs on steroids. Their larvae are yellow and look fuzzy. Larvae are big eaters, despite their size. A huge population could damage a crop, but a few here and there won't hurt a thing.
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